The invention relates to the field of dispensing material and, in particular, to the dispensing of material on the zeptoliter scale. It further relates to apparatus useful in such dispensing.
The controlled delivery of fluids is a key process in nature and in many areas of science and technology, where pipettes or related devices are used for dispensing well-defined fluid volumes. Existing pipettes are capable of delivering fluids with attoliter (10−18 l) accuracy at best. See Meister, A., et al., “Nanodispenser for attoliter volume deposition using atomic force microscopy probes modified by focused-ion-beam milling,” Appl. Phys. Lett. 85, 6260-6262 (2004). Studies on phase transformations of nanoscale objects would benefit from the controlled dispensing and manipulation of much smaller droplets. In contrast to nanoparticle melting whose fundamental pathway has been studied extensively (Frenken, J. W. M. & van der Veen, J. F., “Observation of surface melting,” Phys. Rev. Lett. 54, 134 (1985)), experiments on crystallization, testing classical nucleation theory, are hindered by the influence of support interfaces. Experiments on free-standing fluid drops are extremely challenging. See Egry, I., Lohoefer, G. & Jacobs, G., “Surface tension of liquid metals: Results from measurements on ground and in space,” Phys. Rev. Lett. 75, 4043 (1995).